I think the most recently created character to have achieved very successful and iconic status, at least without directly using similar imagery of a previous hero and is relatively more distinct, is Gambit. I've seen comparisons of Deadpool/Spider-Man, X-23/Wolverine, as well as heroes who seem to gain more recognition specifically because they have familiar mantles, like Kamala Khan and Miles Morales, and while new heroes taking up old mantles definitely happened in the 60s-90s, I still wonder if one could make the solid argument that Marvel is relying more on "hand-me-down mantles" now than compared to the past.